The Hualapai Valley basin is in northwestern Arizona and contains 1,820 square miles. The basin is bounded on the west by the Cerbat and White Mountains, on the east by the Grand Wash Cliffs and Music Mountains, on the south by the Peacock and Hualapai Mountains, and on the north by Lake Mead.

The Hualapai Valley basin-fill sediments range to as much as 6,400 feet thick (Oppenheimer and Sumner, 1980), and have been divided into three separate units: a younger alluvium, an intermediate alluvium, and an older alluvium (Gillespie and Bentley, 1971).

The younger alluvium includes streambed deposits in Hualapai Valley and in various mountain canyons. The unit seldom exceeds 50 feet in thickness, and is composed of silt to gravel-sized particles. The younger alluvium yields small amounts of water to stock and domestic wells in mountain canyons (Gillespie and Bentley, 1971). The igneous and metamorphic rocks, volcanic rocks, and Paleozoic sedimentary rocks are generally non-water bearing. However, fractured and weathered zones in these rocks do provide some water to low-yield wells, and numerous springs and seeps.

In the central part of the valley, the younger and intermediate alluvium are above the water table, and therefore, dry. The intermediate alluvium is a dependable aquifer only along the valley margins where the unit intersects the water table. Well yields from the intermediate alluvium range up to 500 gallons per minute (Gillespie and Bentley, 1971). The intermediate alluvium is made up of coarse-grained sands, silts, and clays.

The older alluvium is the main aquifer in the Hualapai Valley basin. Volcanic rocks are interbedded with the older alluvium in the southern part of Hualapai Valley and form a secondary system (Cella Barr Associates, 1990). The older alluvium can store and transmit large amounts of water; well yields up to 1,500 gallons per minute have been reported (Remick, 1981). Depth to water ranges from 500 to 900 feet below land surface in the central and southern parts of the basin to 300 feet below land surface near Red Lake (Remick, 1981).

Although the Hualapai Valley basin is sparsely populated, 5,000 acre-feet of groundwater were withdrawn from it in 1984 (U.S. Geological Survey, 1986). The City of Kingman has a well field in the southern portion of the valley near the airport that is responsible for most of the withdrawals. The remainder of the pumpage is for stock and domestic uses by the ranches and settlements in the valley. Withdrawals by Kingman alone exceeded 6,000 acre-feet in 1989.

Schmidt and Associates (1993) reported water level declines in the southern part of Hualapai Valley. A well at the southwest edge of the airport had a recorded water level decline of 1.0 feet per year for the period 1986 to 1992. The greatest water level decline recorded was 2.0 feet per year between 1980 and 1991 in a well about three miles northwest of the airport. The average water level decline rate for the basin is 1.4 feet per year (Arizona Department of Water Resources, 1994).

Small water level declines have been recorded over the rest of the Hualapai basin due to the undeveloped nature of the groundwater resources (Celia Barr Associates, 1990). In the vicinity of Hackberry, however, annual water level declines of up to seven feet per year occurred during the 1960’s when the Hackberry wellfield was used as a municipal water supply for Kingman. Municipal use of the wellfield was discontinued after 1969 and water levels near Hackberry have continued to recover (Celia Barr Associates, 1990; Federal Energy Regulatory Commission, 1981).

Recharge to the valley aquifers is from streambed infiltration. Recharge from precipitation on the valley floor is negligible due to high evapotranspiration rates. Freethey and Anderson (1986) estimate that recharge is 4,000 acre-feet per year in the Hualapai Valley basin. Approximately 1,000 acre-feet of that total are underfiow from the Hackberry area, and 3,000 acre-feet are from streambed infiltration (Freethey and Anderson, 1986; Gillespie and Bentley, 1971). However, the Truxton Canyon Water Company’s well field may be intercepting most of the underfiow from the Hackberry area (Remick, 1981). Actual net recharge into the basin may be only 3,000 acre-feet per year.

Groundwater moves from the mountain fronts towards the center of the valley, then flows north and exits the basin as underfiow to Lake Mead (Gillespie and Bentley, 1971). Hualapai Valley is probably in a state of limited groundwater depletion. Outflow is probably between Remick’s (1981) estimate of 2,500 acre-feet per year and Freethey and Anderson’s (1986) estimate of 4,000 acre-feet per year. Total groundwater availability to 1,200 feet below land surface in the basin is estimated to be 5,000,000 acre-feet (Freethey and Anderson, 1986; Arizona Department of Water Resources, 1988).

The chemical quality of water from the older alluvium aquifer in the Hualapai valley generally is good. Total dissolved solids range from 210 to 1,100 milligrams per liter (mg/l); however, in some areas in or near the mountains groundwater is highly mineralized. Total dissolved solids in these areas ranges from 1,430 to 2,365 mg/l (Gillespie and Bentley, 1971). The recommended secondary maximum contaminant level for total dissolved solids in drinking water is 500 mg/l (U.S. Environmental Protection Agency, 1988). Fluoride concentrations in water ranged from 0.1 to 6.5 mg/l (Remick, 1981). High concentrations of sodium chloride may occur in wells near the salt deposit in the area of Red Lake.

Chromium has been detected in several of the water production wells operated by the City of Kingman in the airport area (Cella Barr Associates, 1990; Schmidt and Associates, 1993). In 1982, eight of ten known wells drilled in the airport area contained chromium in excess of the maximum contaminant level of .05 milligrams per liter (Celia Barr Associates, 1990). In 1992, the maximum contaminant level for chromium was raised to .10 milligrams per liter; all of the water sample results for the City of Kingman’s airport area production wells were then under the new maximum contaminant level for chromium (Schmidt and Associates, 1993). Prior water quality studies have noted an increase in chromium below a depth of about 1,000 feet.

Sacramento Valley Basin

The Sacramento Valley basin covers about 1,400 square miles in western Arizona. The entire basin falls within the Basin and Range province. The basin trends in a north-south direction and is bounded on the west by the Black Mountains, on the southwest by the Mohave Mountains, and on the east by the Cerbat and Hualapai Mountains. Elevations range from 8,417 feet above mean sea level at Hualapai Peak to about 500 feet above mean sea level where the Sacramento Wash joins the Colorado River near Topock.

The older alluvium is the principal aquifer in the Sacramento Valley basin. Unconfined conditions are predominant in the aquifer which has an approximate areal extent of 500 square miles. The recoverable groundwater in storage to 1,200 feet is estimated to be 7 million acre-feet (Arizona Department of Water Resources, 1988). Depth to water ranges from over 1,000 feet below land surface in the northern part of the basin north of Highway 68 to less than 100 feet below land surface where the Sacramento Wash enters the Colorado River valley (Rascona, 1991). Saturated thicknesses ranged from 0 to 600 feet (Arizona Department of Water Resources, 1988).

Groundwater declines have occurred in the former Duval Corporation well field south of Highway 68. Now owned by Cyprus Metals Company, this well field exhibits average groundwater level declines of 0.8 feet per year (Arizona Department of Water Resources, 1994). In the Golden Valley area, north of Highway 68, groundwater levels declined 26 feet (an average of 1.2 feet per year) during the period 1979 to 1991. These declines are due to groundwater withdrawals associated with the steady increase of population and the Cyprus Metals Company well field to the south. In 1990, about 370 acre-feet of groundwater was withdrawn from this area north of Highway 68. Little to no water level decline has been recorded in the remainder of the basin (Rascona, 1991; Schmidt and Associates, 1993).

The groundwater in the Sacramento Valley basin generally is of good chemical quality. However, the groundwater located along the base of the mountain ranges tends to have a high mineral content. Total dissolved solids in the range of 1,400 to 2,400 milligrams per liter were reported in samples from areas in and near the Cerbat Mountains (Gillespie and Bentley, 1971). All other chemical constituents within the water are within drinking water standards.

The amount of groundwater pumped from the aquifers has varied over the years. It has ranged from 6,000 acre-feet per year from 1964-1980 to about 2,000 acre-feet per year from 1981-1986 (Steve Rascona, personal commun., 1991). The decline in water use represents the reduction in mining activity at the Mineral Park Mine in the 1980’s. Cyprus Metals Company acquired the Mineral Park Mine from the Duval Corporation in 1986; annual groundwater pumpage has ranged from 400 acre-feet in 1986 to 600 acre-feet in 1990. Although the open pit copper-molybdenum mine and concentrator were on standby in 1989, the precipitation plant has begun operating (Arizona Department of Mines and Mineral Resources, 1988). Water use is expected to increase as the mine becomes more active. Cyprus Metals Company owns the five former Duval wells which have yields of up to 1,000 gallons per minute. Residential water use has been increasing steadily with the population growth in the Golden Valley area. Most wells in the basin are low yield stock and domestic wells. No irrigation wells are present.

The City of Kingman is the main population center in the Sacramento Valley basin, A small portion of the City is on a ridge of fractured and faulted volcanic rocks separating Sacramento Valley and Hualapai Valley basins and a large portion is on the alluvial fill of Hualapai Valley basin. Kingman has developed a well field at the southern end of the Hualapai Valley basin to provide a dependable, long-term source of water supply. The 1989 demand of the City was about 6,000 acre-feet; 450 acre-feet of groundwater were pumped from wells completed in volcanics of the Sacramento Valley basin. In addition to groundwater, the City of Kingman has an available supply of 18,500 acre-feet per annum of Colorado River water under a valid and unused 1968 contract.

The Town of Chloride has been experiencing a severe water shortage and hauls water from Kingman to supplement their needs. Groundwater pumped from fractured granite in the area is insufficient to meet Chloride’s needs, and repeatedly exceeds the maximum contaminant level established for radionuclides.

The principal aquifer receives most of its recharge by infiltration of runoff into the alluvium of the washes and along the mountain fronts. Gillespie and Bentley (1971) estimated that 4,000 acre-feet of water per year are recharged to the main aquifer. Surface discharge from the Sacramento Wash is estimated to be about 500 acre-feet per year (Gillespie and Bentley, 1971).

Big Sandy Basin

The Big Sandy basin consists of approximately 1,900 square miles in northwest Arizona. It is bounded by the Hualapai Mountains to the west, the Mohon Mountains to the south, the Juniper Mountains to the east, and the Peacock Mountains and Cottonwood Cliffs to the north. The Aquarius Mountains run north-south and divide the Basin and Range province to the west from the Central Highlands province to the east. Land surface elevations in the mountainous areas range from 5,000 feet above mean sea level in the Aquarius Mountains in the central part of the basin to a maximum altitude of 8,417 feet above mean sea level at Hualapai Peak in the Hualapai Mountains to the west.

Groundwater occurs in three hydrologic settings: in the floodplain alluvium and upper basin-fill found along the central valley, and in the sedimentary rocks found in the extreme northeastern part of the area.

The floodplain alluvium generally is 30 to 40 feet thick. This unit is an unconsolidated deposit of gravel and sand that underlies the streams and floodplains. Wells greater than 40 feet deep that tap the stream and floodplain alluvium along the Big Sandy River near Wikieup also tap the upper basin-fill. These wells, if properly constructed, can yield as much as 1,000 gallons per minute. As of 1980, there had been no significant changes in water level in the unconsolidated deposits.

Most of the groundwater development has been along the central valley where one of the main water-bearing units is the upper basin-fill. These deposits vary from a loosely-consolidated silty gravel to a sandy silt. The thickness of the upper basin-fill is estimated at 150 to 200 feet in the northern part of the area and about 300 feet near Wikieup and Natural Corrals Wash. The upper basin-fill receives recharge from streamfiow during most of the year. It is estimated that the upper basin-fill is capable of yielding as much as 1,000 gallons per minute of water to wells (Davidson, 1973).

In the east-northeast portion of the Big Sandy basin, a sedimentary layer composed of the Redwall Limestone and the Martin Formation (Arizona Bureau of Mines, 1958) may be a regional aquifer which extends to adjacent areas to the north and the east (Cady, 1981). in the area of the Big Sandy basin where this unit is present, the depths to water range from 32 feet below land surface in the east near Buck Dam to a reported 950 feet below land surface in the northern part of the basin, just south of Rubel Ranch. There are very few wells in this area, therefore, the areal extent of the aquifer cannot be determined.

The Hackberry area, in the north-northeast portion of the basin, is experiencing long-term declines of 1 to 2.5 feet per year (Gillespie and Bentley, 1971; Remick, 1981).

The dissolved-solids concentrations in the Big Sandy basin range from 282 milligrams per liter (mg/l) in the basin-fill southwest of the Peacock Mountains to 2,460 mg/l in Antelope Wash, northeast of the Hualapai Mountains. Fluoride concentrations in this area range from 0.2 mg/l in the Mohon Mountains to 20.0 mg/l along the edge of the basin- fill, east of Hualapai Peak. Overall, the quality of the groundwater in the Big Sandy basin is good, however, the groundwater in much of the area contains fluoride in amounts greater than the maximum contaminant level of 1.4 mg/l. The groundwater in the Big Sandy basin is suitable for irrigation use because it is not highly mineralized and the sodium concentrations generally are smaller than those of calcium and magnesium (Davidson, 1973).

In the past, the primary use of groundwater has been for agriculture, however, since the early 1970’s, groundwater pumped in the Big Sandy area primarily has been used for mining. In 1980, approximately 2,000 acre-feet of groundwater were withdrawn and roughly 95 percent of that water was transported by pipeline to the Bill Williams basin for use in mining operations.